This invention relates generally to the continuous casting of metals on or between moveable endless casting surfaces, and more particularly to a method and apparatus for applying a fluid coating between cast metal and moveable endless casting surfaces.
Various metal casting operations involve the depositing of molten metal to be cast between moveable endless casting surfaces such as belts and wheels, the metal being solidified as it is transported between the moving surfaces and the casting being separated from the moving casting surfaces at a point spaced from the locality of molten metal delivery to the surfaces. In particular, continuous casting processes are known wherein the molten metal to be cast is fed continuously between a rotating water cooled casting wheel and a synchronously driven metal band which engages the circumference of the rotating casting wheel. As the cast metal travels between the rotating casting wheel and the circumferential band, it solidifies and emerges from between the two surfaces as a continuous bar, ready to be rolled or otherwise worked. For purposes of illustration, the present invention will be described with specific reference to its use in a continuous copper bar casting operation such as just mentioned, but it is to be understood that the invention in its broader aspects may be utilized with other metals and in other continuous casting processes that employ moveable endless casting surfaces.
The production of a bar of acceptable quality in a moveable endless surface casting apparatus requires uniform heat extraction from the metal traveling between the casting surfaces. For achievement of this condition, the casting surfaces must be maintained in a substantially flat condition and must not become thermally distorted or warped as a result of contact with the molten metal. In addition, the solidifying metal must not adhere to the casting surfaces.
For these reasons, protection of the casting surfaces against excessive temperatures that might cause thermal distortion of their shape and to facilitate the separation of the cast bar from the casting surfaces in an apparatus of the aforementioned type must be coated with a suitable thermal barrier having heat insulating and other properties, the general concept of which is disclosed in U.S. Pat. No. 3,322,184.
Prior art attempts to solve these problems have not been totally satisfactory. The principal deficiency in the prior art methods has been the failure to uniformly apply thermal barrier to the casting surfaces, thus resulting in undesirable distortion and deterioration of the casting surfaces. Consequently, it has been customary to tolerate distortion and deterioration of the casting surfaces and in some instances, the undesirable segregation of alloying constituents in the cast metal to achieve easy extraction of the cast bar from the casting surfaces. Further, prior art techniques have been unsatisfactory because none have even addressed the problems of coolant contamination and fire hazards which constantly attend the application of coatings to the moving casting surface by present methods.
A variety of devices for applying thermal barriers to casting surfaces have been used in the prior art. These prior art devices have characteristically used various combinations and arrangements of sprays and internally flooded rollers and more recently prior art methods have included the manual application of a thermal barrier paint to the casting surfaces prior to casting and the continuous application of a powder release agent to the casting surfaces during casting. Such methods are cumbersome and require periodic intervals in which the casting machine is inoperative while the thermal barrier is being reapplied to the surfaces.